Epicillin, 6-[D-2-amino-2-(1,4-cyclohexadien-1-yl)acetamido]-3,3-dimethyl-7-oxo-4-thi a-1-azabicyclo[3.2.0]heptane-2-carboxylic acid, is disclosed as a useful, orally administerable antibacterial agent by Weisenborn et al. in U.S. Pat. No. 3,485,819.
Talampicillin, 6-[D-2-amino-2-phenylacetamido]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2 .0]heptane-2-carboxylic acid, 1,3-dihydro-3-oxo-1-isobenzofuranyl ester (i.e. the phthalidyl ester of ampicillin), is disclosed by Ferres et al. in U.S. Pat. No. 3,860,579. Talampicillin is stated to be well absorbed when administered orally and yield high serum levels of the parent penicillin, i.e. ampicillin.
Ferres in U.S. Pat. No. RE 29,650 describe the phthalidyl ester of 6-APA and various ampicillin intermediates wherein the .alpha.-amino group is protected.
Lactonyl esters of various penicillins and cephalosporins are disclosed by Ferres et al. in U.S. Pat. No. 4,036,829. Among the penicillins disclosed are the phthalidyl ester of hetacillin and various substituted pthalidyl esters of ampicillin.
Callander in U.S. Pat. No. 4,072,677 disclose a process for preparing various penicillin esters. Among the disclosed penicillin acyl sidechains is (.alpha.-aminocyclohexadienyl)acetamido and among the ester groups is phthalidyl.
Murakami et al. in U.S. Pat. No. 3,951,954 disclose oxofuryl esters of various penicillins and cephalosporins having an (.alpha.-amino-phenylacetamido) acyl sidechain. Among the compounds disclosed is the phthalidyl ester of ampicillin as note Example 4.
Hetacillin, 6-[2,2-dimethyl-5-oxo-4-phenyl-1-imidazolidinyl]-3,3-dimethyl-7-oxo-4-thia -1-azabicyclo[3.2.0]heptane-2-carboxylic acid, is disclosed by Johnson et al. in U.S. Pat. No. 3,198,804. Hetacillin is prepared by reacting ampicillin with acetone.